strange sql select statement

It's a webbsite using C# and ado.net to access a oracle database.
Below is some piece of the sql select statement that is used and here you
can see form_slag and I wonder
how this is possible. This form_slag looks like a variable.
If I look at this sql select statement just before dataadapter.fill is
executed I see this form_slag just as it is in the select statement below.
What seems very strange to me is where is the actual value for this
form_slag is a given.
This form_slag must have a value before the dataadapter.fill is executed but
it has not or
it must be fetched from the database in some way that I don't understand.

Can anybody explain how this form_slag can be used in the way that it is
used ?